A bolometer is a type of thermal sensor that senses a change in temperature of an object based on a change in electromagnetic radiation emitted by the object. Typically, bolometers are configured to detect radiation in the infrared range, which has a wavelength of approximately three to twelve micrometers (3-12 μm).
Most bolometers include an absorber for detecting/receiving the radiation emitted by the object. Of the various materials available for forming the absorber, metals are not typically considered suitable. This is because in general metals are very good at shielding/reflecting infrared radiations. It was discovered, however, that at ultra-thin layers, for example approximately ten nanometers (˜10 nm), metals act as good absorbers for infrared radiation. Upon absorbing radiation, the ultra-thin layer of metal heats-up and exhibits a change in electrical resistance, which is monitored by external circuitry to sense a change in temperature of an object.
When using an absorber formed from an imperforate ultra-thin layer of metal, the bolometer exhibits a relatively narrow bandwidth and a moderate capacity for absorbing incident radiation. The bandwidth of the bolometer refers to the range of wavelengths that are detectable by the absorber. The capacity for absorption of the bolometer refers to the percentage of incident radiation that is absorbed by the absorber. Ideally, a bolometer absorbs 100% of the incident radiation across a wide bandwidth. Known bolometers, however, do not achieve these ideal specifications.
Accordingly, a need exists to further improve the structure of bolometers to increase the bandwidth and the capacity for absorbing incident radiation, thereby resulting in a more efficient bolometer.